Loss of p47 ^phox Subunit Enhances Susceptibility to Biomechanical Stress and Heart Failure Because of Dysregulation of Cortactin and Actin Filaments

Abstract

Rationale:The classic phagocyte nicotinamide adenine dinucleotide phosphate oxidase (gp91 phox or Nox2) is expressed in the heart. Nox2 activation requires membrane translocation of the p47 phox subunit and is linked to heart failure. We hypothesized that loss of p47 phox subunit will result in decreased reactive oxygen species production and resistance to heart failure.Objective: To define the role of p47 phox in pressure overload-induced biomechanical stress. Methods and Results:

Mechanosensitive Regulation of Cortactin by p47 phox

“…15,16 This phenomenon is dependent on p47 phox but not Nox2. 8 These novel findings underscore the importance of the p47 phox -cortactin axis in the regulation of actin cytoskeletal networks that are indispensable for normal cell function. To understand how p47 phox might act as a cortactin regulator, an appreciation of cortactin biology is necessary.…”

“…In a series of elegant studies using p47 phox -and Nox2-deficient mice to carefully dissect the impact of p47 phox alone versus p47 phox as an integral component of Nox2, the authors show unambiguously that the p47 phox effect is independent of Nox2, Nox activity, or changes in ROS levels because unlike p47 phox -deficient hearts, Nox2-deficient hearts were protected against pressure overload-induced pathological remodeling. 8 Dissecting the ROS-independent mechanisms, whereby p47 phox influences cytoskeletal organization, cortactin, a molecular scaffold for actin assembly, 9,10 was identified as a key player. Such findings challenge the dogma that p47 phox , also known as neutrophil cytosolic factor 1, has, as its sole purpose, the organization and activation of Nox 1,2 and raise the possibility that p47 phox may have pleiotropic functions beyond Nox-derived ROS production.…”

“…[11][12][13][14] In this issue, some of these concepts are further developed to show that in the heart, functionally intact p47 phox is essential for normal cardiac cytoskeletal dynamics and adaptive remodeling in response to biophysical stress and that in its absence there is a predisposition to cardiac failure through dysregulated cortactin signaling and cytoskeletal disorganization. 8 Hence, at least in the setting of biomechanical stress, p47 phox is protective and essential for normal cytoskeletal architecture in the heart, a process that involves N-cadherin, which stabilizes actin and the cytoskeleton. 15,16 This phenomenon is dependent on p47 phox but not Nox2.…”

A Disintegrin and Metalloprotease-17 Regulates Pressure Overload–Induced Myocardial Hypertrophy and Dysfunction Through Proteolytic Processing of Integrin β1

“…13 Male f/f, f/f/Cre, and Cre mice, at 8 to 9 weeks of age, underwent transverse aortic constriction (TAC) to generate pressure overload as previously described. 14,15 Briefly, anesthesized mice underwent thoracatomy, a constriction was made on the aortic arch between the left carotid artery and the brachiocephalic trunk, to the diameter of a 27-gauge needle. The incision was closed in layers and the mouse was allowed to recover on a warming pad.…”

“…15,19 Fibrosis was determined from picrosirius red-stained sections by using Metamorph Basic software as before. 26 Fluorescent staining for integrin β1 and CD31 was performed on OCT-frozen tissue as described.…”